Electroplating of nickel



Patented May 18, 1954 ELE CTROPLATING OF NICKEL Henry Brown, Detroit,Mich, assignor to The Udylite Corporation, Detroit, Mich., a corporationof Delaware No Drawing. Application August 16, 1950, Serial No. 179,873

34 Claims. 1

My invention relates to improvements in the electrodeposition of nickelfrom aqueous acidic baths. It is particularly concerned with theutilization of certain addition agents for the purpose of decreasinggrain size and increasing the luster of the nickel plate or deposit, andit is especially concerned with the production of electrodeposits ofbrilliant, highly lustrous, ductile nickel plates.

I have discovered that the grain size of electrodeposits may bedecreased and the luster of the nickel deposit increased, all in aneffective manner, by the utilization of certain bath-soluble organiccompounds, specifically, certain aliphatic esters of unsaturatedaliphatic polycarboxylic acids, the unsaturation of which acids is duesolely to double bonds. Particularly satisfactory are the methyl andethyl esters of unsaturated aliphatic polycarboxylic acids containingfrom 4 to 8 carbon atoms although excellent results are also obtainedthrough the utilization of certain alkoxy valkyl esters of suchunsaturated aliphatic polycarboxylic acids. The esters Whose utilizationis contemplated by my present invention are those wherein all of thecarboxyl groups of the unsaturated aliphatic polycarboxylic acids areesterified.

The following Table I lists a number of representative esters whose use'falls within the scope of my present invention. It will be understoodthat the solubility of such esters varies. For effective results theyshould be soluble in the aqueous acidic nickel plating bath to theextent i of the order of at least about 0.15 gram per liter.

In general, it is unnecessary to utilize the even ,more soluble ones ofsuch esters in amounts greater than approximately 3 grams per liter. Inall cases, it will be understood that the esters whose use iscontemplated in accordance with the present invention must be soluble inthe aqueous acidic nickel electroplating bath to a degree sufiicient toenable such esters to exert :the effect of decreasing the grain sizeofthe electroplate of nickel and increasing the luster thereof.

2 Table I 00110 grams] Dimethyl fumarate Dimethyl ehlorofumarate.

Di-(Z-methoxy ethyl) Iumarate. Dimethyl maleata... l. Diethyl maleateDimethyl chlorornaleate Dl-(Z-methoxy ethyl) maleate (Di-MethylCellosolve" maleate) Di-(Z-ethoxy ethyDmaleate (Di-Oe1losolve" Maleate)Dimcthyl itaconatel Diethyl itaconate l Di-(2-methoxy ethyl) itaconateDi-(Z-(B methoxyethoxy)ethyhitaconate Dimethyl methylene malonateDimothyl glutaconate Dimethyl mesaconate. Dimethyl citraconate Dimethylcrot Methyl ethyl mal ate Methyl, 2-metl1oxy ethyl fumarate.Di-(2-ethoxy ethyl) fumarate l. Di-(2-ethoxy ethyhitaconate we w weretWt t OOOQOOOOOOQOOD O OOQODQQ Esters of Unsaturated Tricarboxylic AcidsES; mm,

1. Trimethyl ethylenetricarboxylate....v 0. 2-2 2. Trimethyl apropylene, a,o,'y tricarboxylate 0. 2-2 3. Trimethyl iso-aconitate(trimethyl a propylene 0,7,7 tricarboxylate) l 0. 2-2 4. Trimethylaconitate (trimethyl a propylene M8, tricarboxylate) 0. 2-2 5. Trimethylallenetricarboxylata l. 0. 2-2 6. Trimethyl oxalocitraconate 0. 2-2 7.Tri-(Z-methoxy ethyDaconitate 0. 2-2 8. 'lri-(2-methoxyethyl)ethylenetricarboxylate. 0. 2-2

Esters of Unsaturated Tetracarboxylic Acids ig l. Tetramethyl ethylenetetracarboxylate 0.2-2 2. Tetramethyl 5y carboxylate aconitate. 0.2-2 3.Tetramethyl a carboxylate aconitate .l 0. 2-2 4. Tetramethyl adicarboxylate glutaconate 0.2-2

Particularly advantageous are the esters of 2- methoxy ethanol; 2-ethoxyethanol; as, for example, di- (2-methoxy ethyl) iumarate; til-(2-methexy ethyll-maleate; tri-(Z-methoxy ethyl) aconitate; di-(Z-ethoxyethyDmaIeate; di-(2- ethoxy ethyl) fumarate; and also the methyl esterssuch as dimethyl maleate, dimethyl fumarate, trimethyl aconitate, anddimethyl itaconate, used either alone, or in mixtures with one another,or in conjunction with organic sulphurcontaining brighteners, asdescribed hereafter.

I have also discovered that if there is utilized in the plating bath, inconjunction with the aforesaid esters, a small proportion of abrightener of the organic sulfonic, sulfonamide or sulfonimide type,exceptionally brilliant, highly lustrous, ductile nickel plates havingexcellent adherence characteristics to the base metal are obtained.While it has heretofore been known to utilize brighteners of theaforesaid organic sulfonic, sulfonamide and sulfonimide types, as isdisclosed in part, for example, in my prior Patents Nos. 2,191,813 and2,466,677, it should be understood that I do not claim any inventionherein the utilization of such known brighteners per se. So far as thisphase of my invention is concerned, a coaction takes place in thecathode film, the exact nature of which is unknown, involving the esterof the aliphatic unsaturated polycarboxylic acid and the organicsulfur-containing brightener, which produces the unusual and highlyimportant results which are brought about in accordance with this aspectof my invention. In this connection, it may be noted that theutilization of the esters of the aliphatic unsaturated polycarboxylicacids alone or the utilization of the organic sulfur-containingbrighteners alone gives no indication of the remarkably enhanced resultswhich occur when both types of compounds are present in the bath,particularly when utilized in their optimum concentrations. Typicalexamples of organic sulfur-containing brighteners which may be utilizedin accordance with my present invention, in conjunction with the estersof aliphatic unsaturated polycarboxylic acids, are disclosed in my priorPatents Nos. 2,191,813 and 2,466,677 and in Table II.

Table II Optimum Sulfur-Containing Brlghteners 00110.,

grams/liter 1. Benzene sulfonamide 0.1-3 2. Toluene sulfonamides (oandp-) 0.1-2 3. o-Benzoyl sulfimide 0.1-2 4. N-Benzoyl benzene sulfonimide.0.1-1 5. p-Toluene sulfonehioramide.. (1.1-1 6. p-Brom benzenesulfonamidm 0.1-1 7. fi-Chlor o-Benzoyl sulfimido 0.1-1 8. xn-Aldehydobenzene suh'onamidc... 0.1-1 9. Sullomethyl benzene sulfonamide. 0.1-610. Benzene sulfonamidc m-carboxylic am 0.1-3 ll. 7-Aldchydo o-benzoylsulfimlde. 0.1-3 l2. N-Acetyl benzene su1ionimlde 0.1-2 13. Methoxybenzene sulfonamides 0.1-1 l4. Hydroxyrnethyl benzene sulionamide 0.1-215. Vinyl snllonamide 4- 2 l6. Allyl sulfonamide 4-12 17. Benzenesulfonic acids (mono-, di-, and tri-) 1-15 18. p-Brom benzene sulfonicacid 3-6 19. Benzaldehydc sulionie acids (0, m, p). 2-6 20. Dlphenylsulfonc sulionic acid 1-8 21. Naphthalene snlfonic acids (mono-, dl-,and tri-) 1-8 22. Benzene sulfohydroxamic acid 23. p-Ohlor benzenesullonic acid. 1-15 24. Diphenyl snlfonlc acid 1-5 25. nJ-Diphenylbenzene sulionic acid 1-4 26. Z-Chloro-5-sulfobenzaldehydc l-5 27.m-Benzene disnlfonamide. 0.5-1 28. Allyl sulfonic acid 4-12 It will beunderstood that said sulfonic brighteners may be utilized in their acidform or in the form of salts as, for example, nickel, sodium, potassiumor other salts. Especially satisfactory, for use in the practice of mypresent invention, are the compounds of Table II corresponding tonumbers 1, 2, 3; 18, 19, 21 and 28, the latter particularly in the formof their nickel salts. Where the term sulfonic acids is used herein andin the claims, it will be understood that the salts thereof are likewiseincluded.

The compounds of Table II produce bright and mirror-like deposits onbuffed metals such as buffed brass. However, at least in the ordinarycase, they do not accomplish the same results on steel polished withemery or on matte (but unburnt) copper plate of 0.0063"-0.0005"thickness but, rather generally yield plates of somewhat dull and grayappearance in these cases. The compounds of Table I, in the usual case,give a different type of plate than that produced by the compounds ofTable II. The plates produced with the compounds of Table I aregenerally cloudy and milky on buffed or matte metal. The rate ofimprovement of luster of the base or basis metal is much more rapid withthe compounds of Table I, per se, than with the compounds of Table II,per se. If, however, the two difierent types of compounds represented inTables I and II are used together in the baths, as I have indicatedabove, a brilliant mirror-like deposit is obtained even over a mattesurface.

In the usual case, the compounds of Table I tend to be consumed at afaster rate during the electroplating process than the compounds ofTable II. The compounds of Table I, in general, have a faster rate ofreduction at the nickel cathode with respect to the nickel ion, whereasthe compounds of Table II, in general, have'a slower rate, that is, thenickel ion is reduced preferentially in the latter case.

The aqueous nickel platin baths may be of various types but, in allcases, they are acidic in character. The preferred baths are those ofthe Watts type or modifications thereof. The nickel salts may comprisenickel chloride, nickel sulfate, nickel fluoborate, nickel sulfamate, orother nickel salts or mixtures of any two or more of said nickel salts,preferably in conjunction with buffer materials as, for example, boricacid. I prefer to utilize boric acid in the bath as it is, in general,the best cathode film buffer. Other bulfers of acidic character may,however, be employed as, for example, formic acid, fluoboric acid, andthe like, and such may be used either in place of or in conjunction withboric acid. For optimum results, the concentration of the boric acid orits equivalent should be above 30 grams per liter, especially in bathsoperated at somewhat elevated temperatures. The baths may also containvarious supplemental agents such as anti-pitting agents and the like. InTable III, I list preferred embodiments of bath compositions.

As I have indicated previously, the concentration of the Table Icompounds in the bath may range from about 0.2 gram to about 3 grams perliter. For optimum results, a range of about 0.6 gram to 2 grams perliter usually is approximately correct. In certain, and perhaps most,cases, these concentrations are close to saturation for the particularesters utilized. Continuous filtration and the use of surface activeagents to prevent pitting tend to aid in solubilizing at least to acertain extent the compounds of Table I and such procedures are,therefore, recommended in at least most cases. Where the esters of TableI which are selected for use hav an appreciable vapor pressure at thetemperature at which the bath is operated, suitable ventilation shouldbe provided.

Table III BathNTo'. Nis'oienio Niotsneo Hanoi 2 l opmfium 1 AdditionAgents grams/liter grams/liter grams/liter l 300 4D 40 to 50: 2.8 to 4.8Dimethyl fumarate, 2 grams/liter. 2; 300 40 to 75 4O 40 to 65 2.8 to 4.8Di(2-mcthoxy ethyhmaleate, 2 grams/liter plus Benzene sulfonamide, 2 to3 grams/liter and/or o-beuzoyl sulfimide, 0.1 to 2 grams/liter. 3 300 4040 -10 to 65 2.8 to 4.8 Trimethyl aconitate, 2 grams/liter. 4 .l 300 4040 40 to 65 28 to-4.8 Trimethyl ethylene tricarboxylate; 2 grams/literpluso-benzoyl sulfimide, 0.1 to 2 grams/liter. 5 300 40 40 40 to 65 2.8to 4.8 Tetramethyl ethylene tetracarboxylate, 2 grams/ iter. 6 .l, 30040 to 75 4O 40 to 65 2.81.0 4.8 Tetramethyl ethylene tetraearboxylate, 2grams/ liter plus Benzene sullen-amide, 2 grams/liter. 7 to 100 0120 4 00 040 40 to 65' 2.8 to :20 'lrimethyl acouitate, 2 grains/liter.

N1(B F92 100 to 300 The baths can be operated at temperatures rangingfrom about room temperature to almost boilin but, in general, thepreferred temperature is in the range of about 46 degrees C. to 65degrees C. Where the baths are operated at somewhat elevated.temperatures, it will be understood that theesters of the unsaturatedaliphatic polycarboxylic selected should be those which are stable atthe bath temperatures. In general, the baths can be operated at pHvalues ranging from about 2 to about 5.5 but, in the ordinary case, thepreferred p l-l values are from 3.0 to 4.8. The cathode current densityranges are quite variable, a range or" about to several hundred amperesper square foot being utilizable, the optimum depending upon agitation,temperature, and concentration and type of nickel salts utilized in thebath. A good working rang is about to about 80 amperes per square foot.Most of the compounds of Table I function optimumly at pH values ofabout 3.8 to 4.5 and at bath temperatures of about degrees C. to degreeC. Generally speaking, the lower the temperature of the bath, the higherthe pl-l value at which the bath should be operated for obtainin optimumresults.

It should be understood that while certain of the esters of Table I, forexample, dimethyl fumarate, may serve best for the accomplishment of thereduction of grain size and the production of a ductile, lustrous thoughmilky deposit when used. alone, such esters are not necessarily the bestones to achieve, in conjunction with utilization of the organicsulfur-containing brighteners, the production of bright mirror-likedeposits over matte metal surfaces. Thus, for era le. 2. better conjointeffect is produced through the utilization of di-(Z-methoxy ethyl)maleate in conjunction with o-benzoyl sulfimide than with dimethylfumarate in conjunction with o-bensoyl sulfimide. Moreover, thedi-(Z-methoxy ethylhnalcate has the practical advantage over thedimethyl fumarate in that it is less volatile and is easier to handle inrelation to odors, eiiects on the skin and the like.

I have also found that the presence of free 2-methoxy ethanol orZ-phenoxy ethanol or the like in the in concentrations of about 1 to 15grams per liter or even higher help to brighten the medium and lowercurrent density areas, especially when the compounds of Table II arealso present with the compounds of Table I. The free Z-methoxy ethanolor similar compounds may be present in the reaction mixture resultingfrom the processes of preparation of the esters of such. ethanolderivatives, for example, di- (Z-methoxy ethyl) maleate, or they maybeadded as such to the baths.

It will be understood that, from time to time, it is necessary toreplenish the bath to replace losses. due to cathodic processes, todrag-out, and to other causes, in order to maintain the concentrationsor" theadded esters, etc. in operative proportions.

When the unsaturaten esters (Table I) are used Without the organicsulfur compounds (Table II) in the nickel baths (especially the highsulfate type), it is often advantageous to use such sequestering agentsas trimethylamine oc,o:',oc" tricarboxylic acid, ethylene diaminetetra-acetic acid, or their salts (in concentrations up to about 3.grams per liter) tor their beneficial effect in the cathode film inaiding ductilization of the high current density plate especially whenthe DH values are between about 31 .6.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. A bath for the electrcdeposition of nickel comprising an aqueousacidic solution of at least one nickel salt selected from the groupconsisting of nickel chloride, nickel sulfate, nickel iluoborate and.nickel sulfamate, said also containing, in solution, not more than about.5 of at least one bath-soluble fully esterified aliphatic ester of anunsaturated aliphatic polycarboxylic acid, said ester being unsaturatedand the unsaturation of which is due solely to double bonds in the saidacid.

A bath for the electrocleposition of nickel comprising an aqueous acidicsolution of at least one nickel salt selected from the group consistingof nickel chloride, nickel sulfate nickel fluoborate and nickelsuliamate, said bath also containing, in solution, not more than about(3.5% of at least one bath-scluble fully esteriiled aliphatic ester ofan unsaturated aliphatic polycarboxylic acid, said polycarboxylicacidcontaining from 4 to 8 carbon atoms and the unsaturation of which is duesolely to double bonds, and said ester being unsaturated and theunsaturation of said ester being due solely to double bonds in the saidacid.

3. A bath in accordance with claim 2, wherein said ester is di- (2methoxy ethyDmaleate.

i. A bath in accordance with claim 2, wherein said ester is di(Z-methoxy ethyl) iumarate.

5. A bath in accordance with claim 2, wherein said ester isvdi-(Z-methoxy ethyl) itaconate.

6. A bath in accordance with claim 2, wherein said ester isdi-(2.-ethoxy ethybmaleate.

7. A oath in accordance with claim 2, wherein said; ester isdi-(2-ethoxy ethyl) fumarate.

8. A. bath in accordance with claim 2, wherein said ester isdi-(Z-ethoxy ethybitaconate.

9. A. bath in: accordance with claim 2, wherein saidester is at leastone selected from the group consisting of dimethyl esters of maleicacid;

fumaric acid, and itaconic acid.

10. A bath for the electrodeposition of nickel comprising an aqueousacidic solution of at least one nickel salt selected from the groupconsisting of nickel sulfate, nickel chloride, nickel fluoborate andnickel sulfarnate, said bath also containing, in solution, not more thanabout .5% at least one bath-soluble fully esterified aliphatic ester ofan unsaturated aliphatic polycarboxylic acid, said ester beingunsaturated and the unsaturation of which is due solely to double bondsin said acid, and of at least one brightener selected from the groupconsisting of organic sulfonamides, sulionirnides, and sulionic acids.

11. A bath for the electrocleposition of nickel comprising an aqueousacidic solution of at least one nickel salt selected from the groupconsisting of nickel chloride, nickel sulfate, nickel fluoborate andnickel sulfamate, said bath also containing, in solution, not more thanabout 0.5% of at least one bath-soluble fully esterified aliphatic esterof an unsaturated aliphatic polycarboxylic acid, said polycarboxylicacid containing from 4 to 8 carbon atoms and the unsaturation of whichis due solely to double bonds, said ester being unsaturated and theunsaturation of said ester being due solely to double bonds in the saidacid, and not more than about 0.5% of at least one brightener selectedfrom the group consisting of organic sulfonamides, sulfonimides, andsulfonic acids.

12. bath in accordance with claim 11, wherein said ester isdi-(2-methoxy ethyl)maleate.

13. A bath in accordance with claim 11, wherein said ester isdi-(2methoxy ethyl) furnarate.

14. A bath in accordance with claim 11, wherein said ester is di-2-rnethoxy ethyl) itaconate.

15. A bath in accordance with claim 11, Wherein said. ester isdi-(Z-ethoxy ethyhmaleate.

16. A bath in accordance with claim 11, wherein said ester isdi-(Z-ethoxy ethyl) fumarate.

1'7. A bath in accordance with claim 11, Wherein said ester isdi-(Z-ethQX'y ethyl) itaconate.

18. A bath in accordance With claim 11, Wherein said ester is at leastone selected from the group consisting of dimethyl esters of maleicacid, fumaric acid, and itaconic acid.

19. A bath in accordance with claim 2, wherein said ester is trimethylaconitate.

20. A bath in accordance with claim 11, wherein said est-er is trimethylaconitate.

21. A bath in accordance with claim 12, wherein the brightener isbenzene sulfonainide.

22. A bath in accordance With claim 14, wherein the brightener isp-toluene sulionamide.

23. A bath in accordance with claim 18, wherein the brightener iso-benzoyl sulfimide.

24. A bath in accordance with claim 11, wherein said ester isclidZ-methoxy ethyl) maleate, said bath also containing a smallpercentage of Z-methoxyethanol.

25. A bath in accordance with claim 11, wherein said ester isdi-(Z-methoxy ethyl) itaconate, said bath also containing a smallpercentage of Z-methcxyethanol.

26. A method of electrodepositing nickel to obtain a fine-graineddeposit which comprises electrolyzing an aqueous acidic bath containingat least one nickel salt selected from the group consisting of nickelchloride, nickel sulfate, nickel fluoborate and nickel sulfamate, saidbath also containing, in solution, not more than about of at least onebath-soluble fully esterified aliphatic ester of an unsaturatedaliphatic polycarboxylic acid, said ester being unsaturated and theunsaturation of which is due solely to double bonds in said acid.

2'7. A method of electrodepositing nickel to obtain a fine-graineddeposit which comprises electrolyzing an aqueous acidic bath containingat least one nickel salt selected from the group consisting of nickelchloride, nickel sulfate, nickel fiuoborate and nickel sulfarnate, saidbath also containing, in solution, not more than about 0.5% of at leastone bath-soluble fully esterified aliphatic ester of an unsaturatedaliphatic polyoarboxylic acid, said polycarboxylic acid containing from4 to 8 carbon atoms and the unsaturation of which is due solely todouble bonds, said ester being unsaturated and the unsaturation of saidester being due solely to double bonds in the said acid.

28. A method of electrodepositing nickel to obtain brilliant, lustrous,ductile nickel deposits which comprises electrolyzing an aqueous acidicbath containing at least one nickel salt selected from the groupconsisting of nickel chloride, nickel sulfate, nickel fiuoborate andnickel sulfamate, said bath also containing, in solution, not more thanabout .5% of at least one bathsoluble fully esterified aliphatic esterof an unsaturated aliphatic polycarboxylic acid, said ester beingunsaturated and the unsaturation of which is due solely to double bondsin said acid, and of at least one brightener selected from the groupconsisting of organic sulfonamides, sulfonimides, and sulfonic acids.

29. A method of electrodepositing nickel to obtain brilliant, lustrous,ductile nickel deposits which comprises electrolyzing an aqueous acidicbath containing at least one nickel salt selected from the groupconsisting of nickel chloride, nickel sulfate, nickel fiuoborate andnickel sulfamate, said bath also containing, in solution, not more thanabout 0.5% of at least one bathsoluble fully esterified aliphatic esterof an unsaturated aliphatic polycarboxylio acid, said polycarboxylicacid containing from i to 3 carbon atoms and the unsaturation of whichis due solely to double bonds, said ester being unsaturated and theunsaturation of said ester being due solely to double bonds in the saidacid, and not more than about 0.5% of at least one brightener selectedfrom the group consisting of organic sulfonamides, sulfonimides, andsulfonic acids.

30. A composition for addition to an aqueous acidic bath containing atleast one nickel salt selected from the group consisting of nickelchloride, nickel sulfate, nickel iluoborate and nickel sulfamate, toproduce in said bath a concentration of the ingredients of saidcomposition not more than about 0.5%, said composition consisting of atleast one brightener selected from the group consisting of organicsulfonamides, sulfonimides, and sulfonic acids, and, in addition, abath-soluble fully esterified aliphatic ester of an unsaturatedaliphatic polycarboxylic acid, said ester being unsaturated and theunsaturation of which is due solely to double bonds in said acid.

31. An additive for addition to aqueous acidic solutions of at least onenickel salt selected from the group consisting of nickel chloride,nickel sulfate, nickel fiuoborate and nickel sulfamate, to produce insaid bath a concentration of the ingredients of said composition notmore than about 0.5%, said composition consisting of at least onebrightener selected from the group consisting of organic sulfonamides,sulfonimides, and

sulfonic acids, and, in addition, a bath-soluble fully esterifiedaliphatic ester of an unsaturated aliphatic polycarboxylic acid, saidpolycarboxylic acid containing from 4 to 8 carbon atoms and theunsaturation of which is due solely to double bonds and said ester beingunsaturated and the unsaturation of said ester being due solely todouble bonds in the said acid.

32. A composition in accordance with claim 31, wherein said ester is atleast one selected from the grou consisting of dimethyl esters of maleicacid, fumaric acid, and itaconic acid.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,466,677 Brown Aprx 12, 1949 2,523,161 Struyk et a1 Sept. 19,1950

1. A BATH FOR THE ELECTODEPOSITION OF NICKEL COMPRISING AN AQUEOUSACIDIC SOLUTION OF AT LEAST ONE NICKEL SALT SELECTED FROM THE GROUPCONSISTING OF NICKEL CHLORIDE, NICKEL SULFATE, NICKEL FLUOBORATE ANDNICKEL SULFAMATE, SAID BATH ALSO CONTAINING, IN SOLUTION, NOT MORE THANABOUT .5% OF AT LEAST ONE BATH-SOLUBLE FULLY ESTERIFIED ALIPHATIC ESTEROF AN UNSATURATED ALIPHATIC POLYCARBOXYLIC ACID, SAID ESTER BEINGUNSATURATED AND THE UNSATURATION OF WHICH IS DUE SOLELY TO DOUBLE BONDSIN THE SAID ACID.